Etched and ridged polyamide monofilament

ABSTRACT

POLYAMIDE MONOFILAMENT WITH A SURFACE WHICH IS IRREGULARLY RIDGED IN A DIRECTION PREDOMINANTLY TRANSVERSE TO THE LENGTH OF THE FILAMENT, AS WELL AS ETCHED. A METHOD FOR PRODUCTION THEREOF COMPRISING PASSING FILAMENT THROUGH A TUBE UNDER 100-150 P.S.I.G. OF STEAM FOR 0.1-10 SECONDS. SUCH FILAMENTS ARE USEFUL IN BRUSHES AND TEXTILES.

June 20, 1972 E. HANSEN 3,611,381

ETCHED AND RIDGED POLYAMIDE MONOFILAMENT Original Filed June 9, 1959 '2 Sheets-Sheet 1 rm. rm.z

INVENTOR JOHN E. HANSEN AGENT Ju n 20,1972 I I 'KH v 3,611,381

E'IGHED AND RIDGED POLYAMIDE MONOFILAMENT Original Filed June 9, 1969 2 Sheets-Sheet 2 -F|G.5- FIG.

IIIVENTOR JOHN E. HANSEN By Q'W AGENT United States Patent O 3,671,381 ETCHED AND RIDGED POLYAMIDE MONOFILAMENT John Edward Hansen, Wilmington, Del., assignor to E. I. du Pont de N emours and Company, Wilmington, Del. Continuation of application Ser. No. 834,213, June 9, 1969, which is a continuation-in-part of application Ser. No. 616,956, Feb. 17, 1967, and a continuation-in-part of application Ser. No. 673,287, Oct. 6, 1967. This application Sept. 2, 1970, Ser. No. 69,181

Int. Cl. D01f 7/06 US. Cl. 161-180 4 Claims ABSTRACT OF THE DISCLOSURE Polyamide monofilament with a surface which is irregularly ridged in a direction predominantly transverse to the length of the filament, as well as etched. A method for production thereof comprising passing filament through a tube under 100-150 p.s.i.g. of steam for 0.1- seconds. Such filaments are useful in brushes and textiles.

CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation of my copending application Ser. No. 834,213, filed June 9, 1969, now abandoned; which is in turn a continuation-in-part of my copending application Ser. No. 616,956, filed Feb. 17, 1967, now abandoned, and is also a continuation-in-part of my copending application Ser. No. 673,287, filed Oct. 6, 1967, now abandoned.

This invention relates to polyamides, and, more particularly, to monofilament therewith a modified surface.

The art describes various types of surface-modified thermoplastic filaments having pitted, scratched, or longitudinally-ridged surfaces. Such surface modification has been achieved, for example, by mechanical abrasion according to US. Pat. 2,229,347, by caustic treatment according to British Pat. 664,921 and by addition of particulate matter according to British Pat. 951,768.

This invention comprises polyamide monofilament which has a modified surface. The surface is etched as well as irregularly ridged. The ridges are predominantly transverse to the length of the filament, rather than along the length of the filament. Etched as used herein refers to fine structure roughness on the surface of the filament between and across the ridges.

In the figures:

FIGS. 1, 2, and 3 show embodiments of the invention employing polyhexamethylene sebacamide monofilament;

FIG. 4 shows polyhexamethylene sebacamide filament prior to treatment to form the product of this invention;

FIGS. 5, 6, and 7 show embodiments of this invention employing polyhexamethylene adipamide filament; and

FIG. 8 shows polyhexamethylene adipamide filament prior to treatment to form the product of this invention.

The synthetic polyamides which are useful in the filament of this invention are those which are of suflicient molecular weight to be fiber-forming and comprise, for example, polycaprolactam; polyhexamethylene adipamide; polyhexamethylene sebacamide; the polyamide formed from 1,4-(cis)-cyclohexane-bis(methylamine) and adipic acid as described in Bell et al., US. Pat. 3,012,994, issued Dec. 12, 1961; the polyamide from m-xylene diamine and adipic acid as described in Caldwell et al., US. Pat. 2,916,- 475, issued Dec. 8, 1959; the polyamide from 3,5-dimethyl hexamethylene diamine and terephthalic acid as described in Magat, US. Pat. 2,752,328; the polyamide from 2,5- dimethylpiperazine and adipyl chloride as described in Wittbecker, US. Pat. 3,143,527, issued Aug. 4, 1964; coand polyhexamethylene sebacamide wherein the weight adipamide; copolymers of polyhexamethylene adipamide and polyhexamethylene sebacamide wherein the weight percentage of the latter monomer in the copolymer is up to 20% or over and polyamides from bis(4-aminocyclohexyl) methane and dicarboxylic acids containing 6-14 carbon atoms, as described in Bolton et al., US. Pat. 2,- 512,606, issued June 27, 1950. The preferred polyamides are polyhexamethylene adipamide and polyhexamethylene sebacamide.

The filament to be treated to produce the product of this invention can be made using any of the conventional extrusion and drawing techniques. Its diameter can vary widely, for example, in the larger diameter range of about 3-150 mils.

The preferred product of this invention is polyhexamethylene adipamide or polyhexamethylene sebacamide monofilament with a diameter in the range 3150 mils.

To produce the product of this invention, the polyamide filament can be passed through a conventional steam tube in the presence of steam at a pressure in the range of about l00150 p.s.i.g.

The contact time of the filament in the steam tube can be in the range 0.1-10 seconds. The ratio of the speed of the roller at the exit of the steam tube to that of the roller at the entrance to the stream tube should be a least sufficient to take up any slack.

The actual selection of process conditions from within the ranges cited above is dependent upon numerous variables. The filament may be contacted with water prior to its introduction into the steam chamber. Important variables include, but are not confined to, the contact time of the filament in the steam tube, steam pressure and quality, polyamide composition, and filament diameter. The steam pressure and quality and the contact time of the filament in the steam tube must be selected interdependently to achieve the product described herein. For example, with some polyamide compositions, a sufficient degree of surface etching and ridging may not be achieved by selection of the lowest steam pressure and combined with the lowest contact time mentioned herein. Moreover, treatment of some polyamide compositions under a combination of the highest pressure and contact time herein may cause diminution of the sharpness of the ridges formed.

The figures attached are electron microscope photographs of filament taken with a Stereoscan Electron Microscope manufactured by Cambridge Instrument Company, Ltd, London, England. Each photomicrograph is at a magnification of x.

FIGS. 1, 2, and 3 show a ZO-mil diameter filament of polyhexamethylene sebacamide which is etched and ridged according to the present invention. FIG. 4 is identical filament prior to treatment as described herein. FIG. 1 corresponds to Example 4 herein, FIG. 2 to Example 5, FIG. 3 to Example 6 and FIG. 4 to Control A.

FIGS. 5, 6 and 7 show 20-mil diameter polyhexamethylene adipamide monofilament etched and ridged according to the present invention. FIG. 8 is the same filament before treatment to form the product of this invention. FIG. 5 corresponds to Example 11 herein,

' 8 to Control B.

An apparatus conveniently employed to make the product of this invention is a steam tube of any design which permits the maintenance of an environment of high-pressure steam on the filament as it passes continuously through that steam tube. Thus, it is generally desired to employ a tube the construction of which optimizes pres sure leakage from the chamber, for example, one wherein the filament entrance and exit ports are of a cross-sectional area only slightly larger than the cross-sectional area of the filament being passed therethrough to permit turbulence. Steam tubes with low-friction internal surfaces, i.e., with fluorocarbon polymer surfaces, may be used to advantage herein.

Illustrative of the steam tubes in which pressure of steam can be maintained on the filament is one which consists of an outer jacket or pipe and a perforated core. Steam is introduced into the space between the outer pipe and core and passes through the openings and into contact with the filament which continuously enters and exits at either end of the core.

The steam tubes employed in the examples below were composed of Az-inch stainless-steel pipe over an inner stainless tube with a 125-mil outside diameter and an inside diameter of either 55 or 85 mils, depending on the diameter of the filament to be treated. The inner tube had a plurality of A -inch openings drilled radially along its length; Steam was admitted into the outer jacket and passed through the openings, into the core. The overall length of both the outer pipe and core was 6 inches.

The physical properties of the filament reported below were determined by the following methods, on filament which had been stored at 23 C. and 50% relative humidity for at least 2 days after treatment according to this process. The tensile strength for a filament having a diameter (D) in inches and a break load (BL) in pounds, as measured on an Instron Universal Tensile Tester using a 10-inch gap (filament segment) and drawing at 10 inches per minute at 23 C. and 50% relative humidity, was calculated by Equation 1:

Tensile strength (in p.s.i.)

Ultimate elongation (in percent) Tensile modulus was also measured on an Instron Universal Tensile Tester using a 10-inch gap, but drawing at 1 inch per minute. Tensile modulus is calculated by Equation 3, wherein C is distance on the Instron Chart in inches and P is the load in pounds at that point:

( 4PmL Tensile modulus (1n p.s.1.)

The following examples are presented to illustrate but not to restrict the present invention. Parts and percentages are by weight unless otherwise noted.

The contact time referred to in the examples is the time in seconds during which the filament is inside the steam tube, and is calculated by dividing the steam tube length by the linear input speed.

In each example, the monofilament was passed through the steam tube as indicated in Examples 1-7. The conditions of treatment and tensile properties of filament to be treated and of the product are found in Table I.

.. EXAM LESkZ The filament to be treated herein was 20-mil diameter filament of polyhexamethylene sebacamide which had been manufactured in a single-stage draw operation at a draw ratio of 4.0 and then conditioned at 180 C. in air for seconds. The polyamide contained 0.44% nigrosine black azine dye. The properties of the filament before treatment are found in Table I as Control A.

In each example, the untreated monofilament was passed from a supply reel over an input roll, through the steam tube described above which contained 94-96% quality steam (percent by weight-remainder liquid water) at the pressure and'for the contact time indicated in Table .I, and onto a take-off roll revolving at a speed sufficient to. take up any slack which resulted from slight elongation of the filament during steam treatment. However, the filament was not drawn in any of the examples. The various rolls were operated at ambient conditions. The tensile properties of the products are found in Table I.

EXAMPLES 8-14 The filament to be treated herein was 20-mil diameter black polyhexamethylene adipamide. monofilament (containing 0.5% indul'ene dye) which had been manufactured in a single-stage draw operation at a draw ratio of 4.0, and then conditioned at 180 C. in air for 90 seconds. The properties of the monofilament before treatment are found in Table I as Control B.

EXAMPLE 15 The filament to be treated was 3-mil diameterpolyhexamethylene adipamide monofilament which had been manufactured in a single-stage draw operation at a draw ratio of 4.0. The properties of the filament to be treated are found in Table I as Control C.

EXAMPLES 16-18 The filament to be treated was SO-mil diameter polyhexamethylene adipamide monofilament containing 2% lithium bromide, which had been manufactured in a singlestage: draw-operation at a draw ratio of 4.0. The initial propertiesof the filament are found in Table I as Control EXAMPLES 19-21 EXAMPLES 22-23 The filament to be treated was 30-mil diameter polyhexamethylene adipamide monofilament containing2% lithium bromide, which had been made in a single-stage draw operation at a draw ratio of 4.0.. The initial proper ties of the filament are found in Table I as Control F.

EXAMPLES 24-25 A filament of the type set forth in Example 22 which was 22 mils in diameter and of polyhexamethylene adipamide containing 2% lithium bromide (as exemplary of many operable halides). was made by drawing in two stages at a draw ratio of 4.0x thence 1.47 for a total draw ratio of 5.8x. A length of the drawn'filament was treated with 94-96% quality steam at p.s.i.g. for 0.45 second according to the general technique described here inabove. The properties of the monofilament were: break strength 49.3 pounds; elongation at break 16.9%; straight tenacity 120,000 p.s.i. and loop tenacity (6 inch length) 48,000 p.s.i. (measured on an Instron Tester at 24 C. and 55% RH using an elongation rate of 60% /minute). This steam-treated monofilament was dipped in a conventional adhesive resorcinol-formaldehyde latex dip, treated at 325 F. with 1.5% applied stretch for 2.0 minutes, and at 420 F. with 3.0% applied stretch for 0.6 minute. The steam-treated monofils were tested in rubber stock and in tires by normal testing procedures and found to provide excellent adhesion to rubber stock and superior flex life and plunger energy in tires when compared to conventional tire cords or untreated controls. Filaments made with lower draw ratio having a tenacity of at least 110,- 000 p.s.i. and a loop tenacity of at least 33,000 p.s.i. were also found to be satisfactory when tested in tires.

The filament of the present invention exhibits a characteristic surface structure which combines a series of irregular ridges on the surface of the filament, which are predominantly transverse the length of the filament, accompanied by etching or roughening of the surface of the filament between and across the ridges.

In addition to the above qualitative description of the surface of the filament of this invention, the surface ridges thereof may be described in terms of certain measurements described below, and reported for the examples in Table II. The measurements may be made by any con- ,venient method. For Examples l-23, the measurements were made herein using a Zetopan Research Microscope, manufactured by C. Reichert Co. (Austria), fitted with a calibrated eyepiece having a movable cross hair. Surface features of the filament were measured from scale readings on the knurled knob by which the cross hair was moved observing its position relative to the surface feature of the filament. The scale on the eyepiece was calibrated with a 0.01 mm. grating. For Example 24, measurements were made upon the photomicrographs of the product filament with a ruler.

The measurements made on the ridges were the following. Height (H) is the distance from the bottom of a valley to the top of a peak on the filament surface.

6 Width (W) is the width of the ridge measured from trough to trough. Separation (S) is the separation of the ridges measured from peak to peak. The above physical measurements are average values except where a range of values is given. The averages represent measurements which were grouped relatively closely together.

The filament of the present invention is characterized in that, for filament of the diameter range 3-150 mils, H is at least 0.2 mil, preferably at least 0.5 mil. Usually the maximum H in this diameter range is less than several mils. It is obvious that with filament at the lower end of the 3-150 mil range, the maximum H may be less than a mil.

A parameter based on H, W, and S useful in describing quantitatively the ridged nature of the filament of this invention is the ridge factor (F which is calculated as follows:

F 10 H (W/S) F values calculated for the examples reported herein are found in Table II. For those examples where a range is reported for W and S, a range has also been calculated for P The filament of this invention which has a diameter in the range 3-150 mils is characterized by having the F greater than approximately 2, and preferably greater than about 4-5.

ing medium. In addition to the above described improved performance in pickup and retention of solids and liquids, the dull appearance of the filament of this invention renders it appropriate for use in wigs and personal brushes, where there is a subjective preference for a non-glossy surface.

ROUGHENED PRODUC Steam Contact Roll speed Tensile Tensile Ultimate pressure time ratio strength modulus elongation Example (p.s.Lg.) (see) (out/1n) (p.s.i.) (p.s.i.) (percent) TABLE II.MEASUREMENTS ON RID GES IN PRODUCT Filament Separa- Ridge diameter Height Width tion factor Example (mil) (mil) (mil) (mil) (FR) What is claimed is: i I 1. Synthetic polyamide monofilament with a surface structure which is etched and whichhas" irregular ridges in adirection predominantly transverse to theplength'of the filament, said filament having a diameter in the range of from 3-150 mils, and""wherein'the average height of said ridges is at least about 0.2 mil and the average fridge factor is at leastabout 2 mils.

2. Filament according to claim 1 wherein the'average height of said ridges is at least about 0.5 mil and the average ridge factor is at least about 4 to 5 mils.

' 3. Filament according to claim 1 wherein the polyamide is polyhexamethylene adipamide.

4. Filament according to claim 1 wherein the polyamide 'is polyhexamethylene sebacarnide.

References Cited v FOREIGN PATENTS 616,048 1/1949 Great Britain.

1,037,935 7 8/1966 Great Britain.

ROBERT F/BURNETT. Primary Examiner I R. O. LINKER, JR., Assistant Examiner U.s. c1. X.R. r- 

